As the development of electronic technology, electronic devices such as mobile phones, tablets or wearable devices are becoming more and more important in the human's life. There may be a light emitter capable of emitting lights provided in an electronic device. The light emitters can be used for illumination or indication. In the current electronic device, a control element (for example, a button) for controlling the light emitter is usually provided along with the light emitter. If a user wants to start the light emitter, he/she needs to touch the control element. In a case of no lights or no sufficient lights, it is more difficult for the user to accurately position the control element. The operation is inconvenient and the operation speed is not rapid enough.